Moulded-case circuit breaker with improved double-latch mechanism

ABSTRACT

A double latch mechanism for a molded-case circuit breaker suitable for earth-leakage protection, including a centrally pivoted secondary latch lever having one end connected to the plunger of a tripping solenoid. The other end of the secondary latch lever is bifurcated, one projecting portion serving as a latch surface for a pivotable primary latch lever which also has a latch surface engaging a trip lever, and the other projecting portion being coupled to a common trip mechanism. Upon resetting of the circuit breaker, the trip lever drives the common trip mechanism coupled to the secondary latch lever to overcome possible sticking of the solenoid plunger after a severe earth fault.

O United States Patent [151 3,693,121 Carpenter et al. [4 1 Sept. 19, 1972 [54] MOULDED-CASE CIRCUIT BREAKER [56] References Cited WITH IMPROVED DOUBLE-LATCH UNITED STATES PATENTS MECHANISM 3,470,507 9/1969 Hall et al. ..335/ 174 [72] Inventors: Peter E. G. Carpenter, Newbury;

David L. Cook, Swindon, both of Primary Examiner-Harold Broome England Attorney-Harold J. Rathbun [73] Assignee: Square D Company, Park Ridge, 111. l 57] ABSTRACT [22] A double latch mechanism for a molded-case circuit [21] AWL 142,975 breaker suitable for earth-leakage protection, including a centrally pivoted secondary latch lever having one end connected to the plunger of a tripping sole- [30] Foreign Application Priority Data noid. The other end of the secondary latch lever is bifurcated, one projecting portion serving as a latch Jan. 26, 1971 Great Britain ..03,236/71 surface for a pivotabie p y latch lever which also has a latch surface engaging a trip lever, and the other [52] U.S.C|. ..335/l69 projecting portion being coupled to a common trip [5 Int. Clm chanisn Upon resetting of the ircuit breaker the [58] Field sfll'ch trip lever drives the common trip mechanism coupled 335/174, 175, 35 to the secondary latch lever to overcome possible sticking of the solenoid plunger after a severe earth fault.

4 Claims, 6 Drawing Figures PATENTED SE? 19 em SHEET 1 OF 2 lNl/E/VTORS.

PETER E. a. CARPENTER DA V/D L. COOK @J, 21 E H MOULDED-CASE CIRCUIT BREAKER WITH IMPROVED DOUBLE-LATCH MECHANISM This invention relates to an improved double latch mechanism for a molded-case circuit breaker, and more particularly to a double latch mechanism having improved means for cooperation with a common trip mechanism for the several poles of the circuit breaker.

In US. Pat. No. 3,470,507, issued Sept. 30, 1969, there is described a molded-case circuit breaker suitable for earth-leakage protection and having a double latch mechanism operable by a plunger of a solenoid. Although the prior double latch mechanism operates satisfactorily, it has been found to be difficult to manufacture because of critical dimensions locating two adjacent surfaces extending perpendicularly to each other on the secondary latch lever. This disadvantage is overcome by the present invention in which there is provided a secondary latch member having a bifurcated end portion, one projection of which serves as a latch surface, while both projections are adapted to be operably engaged by a link connected to a common trip mechanism. Further, the critically dimensioned surfaces are separated by being disposed respectively on the separate projections of the bifurcated end portion.

It is an object of this invention to provide an improved double latch mechanism for a molded-case circuit breaker.

A further object is to provide a double latch mechanism for a molded-case circuit breaker in which the secondary latch member has one portion serving as a latch surface for the primary latch member and a second portion displaced therefrom each portion serving as a link with a common trip mechanism.

Other objects and advantages of the invention will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is a top view of a two-pole circuit breaker in accordance with this invention;

F IG; 2 is an enlarged view taken substantially along the line 2-2 of FIG. 1 and showing the operating mechanism of an earth-leakage pole portion of the twopole circuit breaker in the closed circuit position;

FIG. 3 is a fragmentary portion of FIG. 2, partially in section;

FIG. 4 is an enlarged view taken substantially along the line 4-4 of FIG. 1 and showing a switch used in the circuit breaker; and FIGS. 5 and 6 are perspective views of the primary and secondary latch levers, respectively.

A two pole earth-leakage sensing circuit breaker embodying the invention is shown in the drawings and comprises a molded case 1 having an earth-leakage pole portion 2, a live pole portion 3, and a cover portion 4, a single side wall of the live pole portion 3 serving as a barrier between the portions 2 and 3. Additional live pole portions may be provided as will become obvious.

FIG. 2 shows the inner mechanism of the earthleakage pole portion 2. With reference to FIG. 2, a trip lever 10 of the earth-leakage pole portion 2 is pivotally mounted to the portion 2 of the case 1 at one of its end portions 11 and is attached near its midpoint (not (not shown) to one end of an overcenter tension spring 12 which is attached at its other end to a movable contact carrier 13.

The contact carrier 13 at its free end portion is U- shaped and the bight thereof carries a movable contact 13a which cooperates with a stationary contact 14 electrically connected to a screw type terminal member 15 by a terminal strap 14a. The other end portion of the contact carrier 13 is pivotally supported between a pair of downwardly extending leg portions 16 of a rocker 17 pivotally supported between the portions 2 and 3 of the case 1. An elongated terminal strap 18 extends through a slot in an end wall of the case portion 2, has its outer end portion electrically connected to a screw-type terminal member 19, and lies along a lower wall of the case portion 2 where its inner end portion is connected to one end of a flexible conductor 20 having its other end electrically connected to the contact carrier 13.

A similar trip lever and associated contact structure is included in the live pole portion 3. The trip levers and associated contact structures of the respective pole portions 2 and 3 are generally like those shown in US. Pat. No. 3,246,098, issued Apr. 12, 1966, and the live pole portion 3 includes a current-responsive tripping means similar to that of the same patent. Each of the trip levers operates in response to operation of the other because of a common trip means hereinafter described.

To ensure the required sensitivity, the latch mechanism of the tripping means in the earth-leakage pole portion 2 is a double-latch mechanism having both a primary latch lever 21 and a secondary latch lever 22. The trip lever 10 is held in the latched position shown in FIG. 2 by engagement of a latching surface 10a on the free end thereof with the primary latch lever 21 which is pivoted near its upper end portion 21a by means of a pair of opposing ears 21b resting on arms 23a of a bracket 23. A helical spring 24 surrounds the upper end portion 21a of the primary latch lever 21 and urges the primary latch lever in a clockwise direction as viewed in FIG. 2.

The trip lever 10, its associated overcenter spring 12, and the primary latch lever 21 are so arranged that the free end of the trip lever 10 bears against the primary latch lever 21 in a manner tending to swing the latch lever 21 counterclockwise about its pivot against the bias of the spring 24 by cam action away from obstructing relationship with the path of movement of the trip lever 10 toward its tripped position. To this end, the latching surface 10a on the free end of the trip lever 10 is disposed in a window 25 (FIGS. 3 and 5) of the primary latch lever 21. A generally U-shaped latch plate 26 of thin metal with good wearing properties has its bight portion received in the window 25 and disposed in spaced relationship to a side face 21c of the primary latch lever 21 facing the trip lever 10. Outwardlyturned free end portions of opposite leg portions of the latch plate 26 extend along the side face 210, the lower of the outwardly-turned free end portions being secured thereto. The latch surface 10a of the trip lever 10 rests against a portion of the latch plate 26 overlying a corner defined by the side face 210 and a bottom wall of the window 25. The latch surface is so inclined relative to the latch plate 26 and to the free end portion of the primary latch lever 21 that the overcenter spring 12 exerts a moment of force in a direction urging the primary latch lever 21 to swing away from the trip lever 10in a counterclockwise direction as above noted. The

trip lever thus tends to free itself from engagement with the primary latch lever 21 and to reach the tripped position under the bias of the overcenter spring 12.

The secondary latch lever 22 normally prevents the trip lever 10 from moving to its tripped position by preventing movement of the primary latch lever 21 in the counterclockwise direction as urged by the trip lever 10, and is in the form of a crank pivotally mounted near its longitudinal midpoint on a projection 27 of the case portion 2. The projection 27 is received within an aperture 22d (FIG. 6). The lever 22 is biased clockwise, as viewed in FIGS. 2 and 3, by a helical spring 28 mounted within a recess in the case portion 2 on the inner side of the pivot axis for the lever 22. The lever 22 has a pair of inwardly directed spaced arms 29 and 30. A latch surface 29a (FIG. 6) on an inner free end portion of the arm 29 normally engages a projection 21d (FIG. 5) on the free end portion of the primary latch lever 21 and prevents the primary latch lever 21 from rotating counterclockwise, as viewed in FIGS. 2 and 3. An upper surface 30a of the arm 30 rests against the upper surface of a notch 21c provided in the free end portion of the primary latch lever 21 to limit clockwise rotation of the secondary latch lever 22.

An outer free end portion 220 of the secondary latch lever 22 is connected to a reciprocable armature or plunger 31 of an earth-leakage sensing solenoid 32 disposed between the primary latch lever 21 and an end wall of the case portion 2. The axis of the solenoid 32 extends generally in the same direction as the longitudinal axis of the primary latch lever 21. In addition to the plunger 31, the solenoid 32 comprises a coil 34 wound on a spool 35 and positioned within a generally U-shaped magnetic core member 36. The bracket 23 is mounted on the member 36.

The coupling of the solenoid plunger 31 to the secondary latch lever 22 is accomplished by reception of the tab 220 on the outer end portion of the secondary latch lever 22 in an annular groove 31a of the plunger 31 as shown most clearly in FIGS. 2 and 3.

The engagement of the surface 3011 with the surface 21c on the primary latch lever 21 limits the clockwise motion of the secondary latch lever 22 and thereby determines the air gap between the upper end of the solenoid plunger 31 and the core member 36. This largely determines the ampere-turn level at which the earth-leakage pole portion 2 trips. It should also be noted that the location of the top edge of the surface 290 determines the amount of overlap with the projection 21d and thus the reliability with which the earthleakage pole 2 will trip at a given ampere turn level without being inadvertently tripped by mechanical shocks.

An earth-leakage sensing means 37 (FIG. 4) is pro- A test means for the earth-leakage sensing means 37 is provided by a push-to-test switch 40 contained within a housing 41 formed integrally with the earth-leakage pole portion 2 and having a detachable molded cover 41a. The push-to-test switch 40 comprises a switch contact portion 42 including the movable bridging contact 43 and two stationary contacts 44 and 45, and a plunger 46 to operate the switch contact portion 42.

The plunger 46 is generally L-shaped, a short leg portion 46a serving as the test button for test switch 40, and a long leg portion 46b serving as the operating stem for the test switch 40.

The plunger 46 is partially received within the case portion 2, the push-button portion 460 being partially received in a recess 47 extending transversely of the pole portion 2, and the stem portion 46b being received in a recess 48 extending partially down the front wall of the pole portion 2, as viewed in FIG. 4.

The push-button portion 46a has a shoulder portion 460 underlying a flange portion 47a of the opening of the recess 47 to limit the upward movement of the plunger 46 and an opposite shoulder portion 46d overlying the edge portion of the opening of the recess 47 to limit the downward movement of the plunger 46. Also, the stem portion 46b is narrowed near its point of connection to the portion 46a to provide a downwardlyfacing shoulder portion 46e which overlies the top surface of the integral molded housing 41 to provide a further limit for the downward movement of the plunger 46.

The bridging contact 43 is biased upwardly, as

viewed in FIG. 4, by a spring 50 which has one end vided to sense excessive ground-leakage and trip the seated against the internal molding of the housing 41 and the other end seated against the bottom surface of the central portion of the bridging contact 43. The cover 410 is held on the housing 41 by self-tapping screws 51 threaded into the outer wall of the case portion 2.

The free end of the stem portion 46b has two spacedapart portions 46g 46h on its extreme end portion which are outwardly offset for reception within complementary grooves in the test switch 40, and are positioned respectively on opposite sides of the spring 50 in the housing 41. The portions 46g and 46h guide the reciprocal movements of the plunger 46 with respect to the test switch 40. Further, the free end portion of the stem portion 46b has an outwardly offset projection 46f which engages the top surface of the central portion of the bridging contact 43 to provide for the downward movement of the bridging contact 43, as viewed in FIG. 4, when the plunger 46 is depressed to test the earth connection of the circuit breaker.

One end portion of the bridging contact 43 has a contact node 43a normally in engagement with the stationary contact 44 to form a normally closed connection therewith, the contact 44 being positioned on the end portion of a terminal strap 53. The other end portion of the bridging contact 43 has a contact node 43b disposed in a predetermined spaced relationship with a contact node 55a disposed on the end portion of a terminal strap 55. The pair of nodes 43b and 55a constitute a spark gap serving as a lightning arrestor for protection of the coil 34, and the spacing is determined by the thickness of a spacing projection 57 provided on the case portion 2.

The terminal straps 55 and 53 have the earth-connected and frame-connected terminals 38 and 39, respectively, connected to their opposite end portions from the stationary contacts 55a and 44, respectively.

' The coil 34 is electrically connected to the earth terminal 38 by the lead 34a, which is permanently connected to the terminal strap 55. The coil 34 is electrically connected to the frame terminal 39 in the normally closed position of the test switch 40 by the lead 34b, which is permanently connected to the bridging contact 43, the connection being completed through the stationary contact 44 and terminal strap 53.

The stationary contact 45 is connected through a resistor 58 and a connecting lead 59 to a terminal strap (not shown) of the live pole portion 3 corresponding to the terminal strap 18 of the earth-leakage pole portion 2. The lead 59 is connected to the stationary contact 45 in the housing 41 for the test switch 40, extends through an opening in the outer wall of the case portion 2 to connect to the resistor 58, which is positioned within the case portion 2, and further extends through the side wall of the live pole portion 3 to connect to the terminal strap (not shown) of the live pole portion 3 corresponding to the terminal strap 18 of the earthleakage pole portion 2.

When the plunger 46 is fully depressed against the bias of the spring 50, the portion of the bridging contact 43 having the movable contact node 430 is electrically connected to the stationary contact 45, thus connecting the earth connection e through the coil 34, movable bridging contact 43, stationary contact 45, and resistor 58 to the power terminal of the live pole portion 3. This connection causes tripping of the circuit breaker if there is a proper electrical connection between the terminal of the coil 34 and the lead 34a to earth. Thus, the continuity of the solenoid circuit and the adequacy of the earth connection can be tested.

The common trip means includes a common trip crossbar or trip cam key 61 carried by a pair of trip cams pivotally mounted respectively between the side walls of the respective pole portions 2 and 3 generally as in U.S. Pat. No. 2,889,428, issued on June 2, 1959, such as a trip cam 62 of earth-leakage pole portion 2. It will be understood that the trip cam (not shown) of the live pole portion 3, upon rotation by the trip cam key 61, directly engages the latch means of its associated current responsive tripping means, as in U.S. Pat. No. 2,889,428, to move the latch means and cause tripping of the associated trip lever.

The trip lever carries a pin 10b adjacent the trip cam 62 and a pin 100 on the opposite side of the rocker 17 from the pin 10b. A biasing spring 63 is secured around the trip cam 62 and has an end portion 63a cooperable with the pin 10b for a purpose hereinafter described. The live pole portion 3 is provided with pins (not shown) similar to the pins 10b and 10c and with a spring (not shown) similar to the spring 63.

The live pole portion 3 is provided with a pivotable operating handle 64 integral with a rocker (not shown) corresponding to the rocker l7 and tied thereto for movement integrally therewith by a tie bar 17a. Movement of the handle 64 thus operates both rockers to move the respective pivotal connections of the contact carriers thereto, such as contact carrier 13, across the lines of action of the respective associated springs, such as the spring 12, and thereby move the contacts, such as the contact 13a, to ON or OFF position. Further, after the circuit breaker has tripped, the handle 64 may be moved to cause the leg portions of the rockers, such as the leg portions 16, to engage and move the pins, such as the pin 10c, to relatch the trip levers, such as the trip lever 10.

The earth-leakage pole portion 2 is provided with a I generally U-shaped trip link 65 having one leg portion pivotally mounted in the trip cam 62 and the other leg portion connected to the secondary latch lever 22 by a lost-motion type connection and positioned to engage a hook-like projection 30b at the inner free end portion of the arm 30 of the secondary latch lever 22 for resetting the earth-leakage pole portion 2 as hereinafter described.

Upon the occurrence of a fault or overload condition in the live pole portion 3 and the release of the trip lever, corresponding to the trip lever 10, by its associated current responsive tripping means, the pin corresponding to pin 10b strikes the trip cam corresponding to the trip cam 62 and causes rotation of the common trip bar or trip cam key 6] counterclockwise as viewed in FIG. 2. The trip cam 62 also rotates counterclockwise, and the leg portion of the trip link 65 moves away from the arm 30 and into engagement with the arm 29 to rotate the secondary latch lever 22 counterclockwise and move the latch surface 29a away from the projection 21d of the primary latch lever 21, resulting in the tripping of the trip lever 10 as explained hereinbefore. The tripping of the trip lever 10 moves the line of action of the spring 12 across the pivotal connection of the contact carrier 13 to the rocker 17, causing the rocker 17 to rotate clockwise as viewed in FIG. 2 and the contact carrier 13 to rotate counterclockwise to move the movable contact 13a out of engagement with the stationary contact 14. The tripping of the trip lever in the live pole portion 3 opens the contacts thereof in a similar manner.

Upon sufficient energization of the coil 34 in the earth-leakage pole portion 2 due to current flowing in the earth connection, the plunger 31 moves upwardly, as viewed in FIGS. 2 and 3, together with the tab 22c of the secondary latch lever 22, to rotate the secondary latch lever 22 counterclockwise and move the latch surface 290 away from the projection 21d of the primary latch lever 21, resulting in tripping of the trip lever The motion of the trip lever 10 causes the pin 10b to strike the trip cam 62 and rotates the trip cam 62 and the trip cam key 61 counterclockwise. The trip cam in the live pole portion 3 also rotates counterclockwise and moves the latch means of its associated current responsive tripping means, as in U.S. Pat. No. 2,889,428, resulting in tripping of the trip lever in the live pole portion 3.

The spring 28 is designed to control the pick-up of the plunger 31 upon energization of the coil 34 and is not necessarily strong enough to overcome sticking of the plunger 31 should sticking thereof occur after a severe earth fault. By the present invention, however, sticking of the plunger 31 is overcome by the resetting of the circuit breaker. Thus, as the handle 64 is moved to engage the leg portions 16 of the rocker 17 with the pin 10c and move the trip lever 10 back to latched position, the pin 10b engages the end portion 63a of the spring 63 and turns the trip cam 62 clockwise to pull the trip link 65 upwardly into engagement within the hook portion 30b of the arm 30 and turn the secondary latch lever 22 clockwise, thereby pulling the plunger 31 outwardly against any stricking forces.

The surfaces 29a and 30a (FIG. 6) of the secondary latch lever 22 are critical surfaces which must be accurately machined. The accurate machining can be readily accomplished in the present invention, in which the two critical surfaces are disposed respectively on the two different arms 29 and 30, rather than being disposed on a single arm in an adjacent relationship in which they form an L-shape, as in prior constructions.

We claim:

1. A molded-case circuit breaker comprising a pair of separable contacts, a pivotally mounted releasably latchable trip lever releasable to effect separation of the contacts, a pivotally mounted primary latch lever normally releasably latching the trip lever, a secondary latch lever pivotally mounted generally centrally thereof and having a bifurcated end portion providing a pair of spaced arms, one of said arms providing a latch surface normally releasably latching said primary latch lever, the other of said anns of said secondary latch lever providing a surface normally engaging a portion of said primary latch lever to limit pivotal movement of said secondary latch lever, means to engage the other of said arms for resetting the circuit breaker, a sensing coil, and a plunger operable by said coil upon passage of sufficient fault current therethrough, said plunger being connected to the other end portion of said secondary latch lever.

2. An electric circuit breaker comprising a molded case having a pair of side-by-side compartments respectively housing a live pole and an earth-leakage sensing pole, each of said poles including a pair of separable contacts, a pivotally mounted releasably latchable trip lever releasable to effect separation of the contacts, a pivotally mounted trip cam, a common trip crossbar extending transversely of said compartments and keyed to the trip cams for rotation integrally therewith, and said earth-leakage sensing pole including a pivotally mounted primary latch lever normally releasably latching the respective trip lever, a secondary latch lever pivotally mounted generally centrally thereof and having a bifurcated end portion providing a pair of spaced arms, one of said arms providing a latch surface normally releasably latching said primary latch lever, the other of said arms of said secondary latch lever providing a surface normally engaging a portion of said primary latch lever to limit pivotal movement of said secondary latch lever, a trip link pivotally connected adjacent one end portion to the respective trip cam and having a lost-motion type connection adjacent the other end portion to said secondary latch lever between said arms thereof, an earth-leakage sensing coil, and a plunger operable by said coil upon passage of sufficient earth-leakage current therethrough, said plunger being connected to the other end portion of said secondary latch lever.

3. An electric circuit breaker as claimed in claim 2, wherein the other of said arms of said secondary latch lever is provided with a hook-like projection engageable by said trip link.

4. An electric circuit breaker as claimed in claim 2, wherein said earth-leakage sensing pole includes a biasing spring on the respective trip cam, and a pin carried by the respective trip lever and engageable with said biasing spring upon resetting of the trip lever after tripping to turn said trip cam and pivot said secondary latch lever by means of said trip link and thereby loosen said plunger in case of sticking thereof after a severe earth fault. 

1. A molded-case circuit breaker comprising a pair of separable contacts, a pivotally mounted releasably latchable trip lever releasable to effect separation of the contacts, a pivotally mounted primary latch lever normally releasably latching the trip lever, a secondary latch lever pivotally mounted generally centrally thereof and having a bifurcated end portion providing a pair of spaced arms, one of said arms providing a latch surface normally releasably latching said primary latch lever, the other of said arms of said secondary latch lever providing a surface normally engaging a portion of said primary latch lever to limit pivotal movement of said secondary latch lever, means to engage the other of said arms for resetting the circuit breaker, a sensing coil, and a plunger operable by said coil upon passage of sufficient fault current therethrough, said plunger being connected to the other end portion of said secondary latch lever.
 2. An electric circuit breaker comprising a molded case having a pair of side-by-side compartments respectively housing a live pole and an earth-leakage sensing pole, each of said poles including a pair of separable contacts, a pivotally mounted releasably latchable trip lever releasable to effect separation of the contacts, a pivotally mounted trip cam, a common trip crossbar extending transversely of said compartments and keyed to the trip cams for rotation integrally therEwith, and said earth-leakage sensing pole including a pivotally mounted primary latch lever normally releasably latching the respective trip lever, a secondary latch lever pivotally mounted generally centrally thereof and having a bifurcated end portion providing a pair of spaced arms, one of said arms providing a latch surface normally releasably latching said primary latch lever, the other of said arms of said secondary latch lever providing a surface normally engaging a portion of said primary latch lever to limit pivotal movement of said secondary latch lever, a trip link pivotally connected adjacent one end portion to the respective trip cam and having a lost-motion type connection adjacent the other end portion to said secondary latch lever between said arms thereof, an earth-leakage sensing coil, and a plunger operable by said coil upon passage of sufficient earth-leakage current therethrough, said plunger being connected to the other end portion of said secondary latch lever.
 3. An electric circuit breaker as claimed in claim 2, wherein the other of said arms of said secondary latch lever is provided with a hook-like projection engageable by said trip link.
 4. An electric circuit breaker as claimed in claim 2, wherein said earth-leakage sensing pole includes a biasing spring on the respective trip cam, and a pin carried by the respective trip lever and engageable with said biasing spring upon resetting of the trip lever after tripping to turn said trip cam and pivot said secondary latch lever by means of said trip link and thereby loosen said plunger in case of sticking thereof after a severe earth fault. 